Help!! My samsung galaxy j5 isn't sleeping...permanently on even when locked manually!!!

[Jerry_jnr]

My Samsung Galaxy J5 is no longer SLEEPING. I reduced the sleep time to 15 secs and after 15secs it just locks and unlocks in about a 1/4 of a second. It's frustrating. It is killing my ba3 dangerously. When I lock it, it just unlocks again in a 1/4 of a second. I introduced a pattern and it's still acting that way. I've performed a hard reset still no luck. Pls help..it was a gift.